Single-stage conversion device integrated with Buck-Boost and AHB flyback circuits

Abstract

The utility model provides a single-stage conversion device integrated with a Buck-Boost circuit and an AHB flyback circuit. The single-stage conversion device is characterized in that the single-stage conversion device comprises the Buck-Boost circuit and the AHB flyback circuit; the Buck-Boost circuit comprises two switch tubes Q1 and Q2, and one switch tube Q2 is multiplexed as an upper tube of the AHB flyback circuit. The single-stage conversion device integrated with the Buck-Boost and AHB flyback circuits is small in stress, has obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application.

Description

Technical Field

[0001] This utility model relates to power converters, and more particularly to a single-stage converter device integrating Buck-Boost and AHB flyback circuits. Background Technology

[0002] With the rapid development of semiconductor technology, fourth-generation LED light sources have been widely adopted and used. Compared with traditional light sources, LEDs have many unparalleled advantages, such as long lifespan, high efficiency, low power consumption, high brightness, and small size, making their application in the lighting field particularly prominent. An LED lighting system consists of two parts: the LED driver and the LED luminaire, with the LED driver being the core component. High-efficiency, energy-saving, high-power LED drivers have become an important research direction in the industry.

[0003] High frequency and miniaturization are important design parameters for switching power supplies. If the power supply operates in hard-switching mode, increasing its switching frequency will result in significant switching losses, reducing the system's conversion efficiency. Therefore, soft-switching technology, which aims to reduce switching losses, has become a major research hotspot in the field of power electronics.

[0004] Resonant converters, including series, parallel, and series-parallel resonant converters, are common soft-switching converters. With proper design, resonant converters can achieve zero-voltage turn-on of the switching transistors and zero-current turn-off of the secondary rectifier diodes over a wide load range, thereby reducing switching losses and improving efficiency. The AC-DC converter uses a Buck-Boost topology, operating in discontinuous mode and automatically implementing PFC (Power Factor Correction). It is a single-switch, low-order boost-and-slow converter circuit that allows for adjustable DC bus voltage, reducing stress on the downstream LLC switching transistors and capacitors.

[0005] There are two main technical solutions in the existing technology: 1. High-power is a two-stage solution, with the first stage Boost achieving power factor correction and voltage regulation, and the second stage DC-DC (isolated and non-isolated topology) achieving output voltage regulation (and electrical isolation, etc.). This solution is technically mature, but the system is complex, costly, and inefficient. 2. Low-power is a single-stage PFC flyback solution, which achieves both input power factor correction and output voltage regulation in a single stage. It is mainly used in low-power LED driver power supplies. This solution is technically mature, simple, low-cost, and efficient, but it has obvious power frequency ripple (which can cause LED flickering), a narrow input voltage range, and lacks a bus capacitor, which can lead to lightning surge problems. Utility Model Content

[0006] The main technical problem to be solved by this utility model is to provide a single-stage converter that integrates Buck-Boost and AHB flyback circuits, which has low stress and obvious advantages in thermal design and efficiency, and is more convenient for product development in practical applications.

[0007] To solve the above-mentioned technical problems, this utility model provides a single-stage converter integrating Buck-Boost and AHB flyback circuits, including a Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit includes two switching transistors Q1 and Q2, and one of the switching transistors Q2 is multiplexed as the upper transistor of the AHB flyback circuit.

[0008] In a preferred embodiment: the switching transistors Q1 and Q2 are simultaneously turned on or off.

[0009] In a preferred embodiment, the AHB flyback circuit further includes a lower transistor Q3, which has the opposite state to that of Q1 and Q2.

[0010] In a preferred embodiment: the switching transistors Q1, Q2 and the lower transistor Q3 are controlled by PWM or PFM.

[0011] In a preferred embodiment, a rectifier bridge is also included, with its AC input terminal connected to an AC power supply and its DC output terminal connected to a high-frequency transformer T1 via the Buck-Boost circuit and the AHB flyback circuit.

[0012] In a preferred embodiment: the two ends of the secondary winding of the high-frequency transformer T1 are connected through a diode D6 and a resistor R1; the resistor R1 is connected in parallel with the capacitor C2.

[0013] In a preferred embodiment: one end of the primary winding of the high-frequency transformer T1 is connected to a resonant circuit consisting of an inductor Lr and a capacitor Cr connected in series.

[0014] In a preferred embodiment: the resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

[0015] In a preferred embodiment: the switching transistors Q1, Q2 and the lower transistor Q3 are power MOSFETs.

[0016] Compared with the prior art, the technical solution of this utility model has the following beneficial effects:

[0017] This invention provides a single-stage converter integrating Buck-Boost and AHB flyback circuits. Two MOSFETs are incorporated into the Buck-Boost circuit, which are then reused as the upper transistor Q2 in the AHB flyback circuit. The voltage stress on the switching transistor Q2 is significantly reduced, while the increased stress on the switching transistor Q1 equals the input voltage. Therefore, transistor selection is more advantageous, allowing for the selection of cost-effective 500V switching transistors. Two fewer power diodes are also eliminated from the main circuit, thus reducing the cost of power semiconductor devices. Furthermore, the operating principle of the AHB flyback circuit is exactly the same as that of a conventional AHB flyback circuit. Q2 and Q3 can achieve ZVS across the entire load range, exhibiting a wide gain variation range and enabling wide voltage input / output. It also offers significant advantages in thermal design and efficiency, facilitating product development for practical applications. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of a preferred embodiment of the present invention;

[0019] Figure 2 This is a timing diagram of a preferred embodiment of the present invention;

[0020] Figures 3-8 The following are equivalent circuit diagrams of the preferred embodiments of this utility model in various modes. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0022] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped with", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0024] refer to Figure 1 This example provides a single-stage converter integrating Buck-Boost and AHB flyback circuits, including a rectifier bridge, Buck-Boost circuit, AHB flyback circuit, high-frequency transformer T1, and load R1;

[0025] The rectifier bridge is a full-bridge rectifier, consisting of four diodes D1, D2, D3, and D4. The AC input of the rectifier bridge is connected to an AC power supply, and the DC output output is a pulsating DC current. The positive terminal of the DC output is connected to the cathode of diode D5, and the anode of diode D5 is connected to one end of the primary winding of the high-frequency transformer T1. The negative terminal of the DC output is connected to the other end of the primary winding of the high-frequency transformer T1 through the switching transistor Q1, the high-frequency capacitor Cr, and the inductor Lr.

[0026] The cathode of diode D5 is also connected to the anode of diode D5 through inductor L1 and electrolytic capacitor C1; the same-name terminals of inductor L1 and electrolytic capacitor C1 are also connected to the high-frequency capacitor Cr through switch Q2, and the anode of diode D5 is also connected to the high-frequency capacitor Cr through switch Q3.

[0027] One end of the secondary winding is connected to the other end through diode D6 and resistor R1, and resistor R1 is connected in parallel with capacitor C2.

[0028] The switching transistors Q1, Q2, and Q3 are power MOSFETs. The aforementioned single-stage converter integrating Buck-Boost and AHB flyback circuits integrates the Buck-Boost circuit and the AHB flyback circuit together, and reuses MOSFET Q2, so that MOSFET Q2 serves as both the switching transistor of the Buck-Boost circuit and the upper transistor of the AHB flyback circuit.

[0029] In terms of control, Q1, Q2, and Q3 employ PWM / PFM control. Q1 and Q2 are simultaneously turned on and off, while Q3's drive complements that of Q1 and Q2. D5 and D6 are power diodes used to rectify the high-frequency AC voltage of the secondary winding of T1 into DC. L1 and Lr are high-frequency inductors, C1 and C2 are electrolytic capacitors, and Cr is a high-frequency capacitor. T1 is a high-frequency transformer.

[0030] The operation is divided into the following 6 modes:

[0031] Mode 1 [t0~t1]: Before t0, the current i in inductor L1 L The voltage has dropped to 0. Simultaneously, because the body diode of Q2 is conducting, at time t0, Q2 is turned on with zero voltage and zero current, and Q1 is turned on with zero current. in The Buck-Boost inductor L1 is charged by switches Q1 and Q2, and the current i in inductor L1 is... L With slope u in / L1 increases linearly. Simultaneously, the DC bus capacitor C1 provides energy to the AHB flyback circuit through the switching transistor Q2. During this stage, the secondary-side rectifier diode D6 in the AHB flyback circuit is reverse-biased and cut off, storing the input energy in Lm and Lr, and the magnetizing current i Lm Equal to the resonant current i Lr The voltage rises linearly. At this time, the output capacitor C2 supplies power to the output load R1.

[0032] Mode 2 [t1~t2]: At time t1, Q1 and Q2 are turned off, entering the dead time. The current in inductor L1 reaches its maximum and begins to discharge. Its current i L The DC bus capacitor C1 is charged through power diode D5, and the current i in inductor L1 is... L The excitation current i decreases linearly. Lm The junction capacitance of Q2 is charged, and the junction capacitance of Q3 is discharged until the voltage across the junction capacitance of Q3 drops to zero. At this time, the output capacitor C2 continues to supply power to the output load R1.

[0033] Mode 3 [t2~t3]: At time t2, the resonant current i Lr All current flows through the body diode of switching transistor Q3, satisfying the zero-voltage turn-on condition, and Q3 is turned on. The secondary rectifier diode D6 is turned on, and the energy stored in Lm is transferred to the secondary side, charging the output capacitor C2 and supplying power to the output load R1. Simultaneously, the voltage across the primary winding of the transformer is clamped at -nVo, and the magnetizing current i... Lm As the linear decrease occurs, the resonant inductor Lr and the resonant capacitor Cr begin to resonate.

[0034] Mode 4 [t3~t4]: At time t3, the current i in inductor L of the Buck-Boost circuit. L The current drops to zero. Q3 continues to conduct, and the resonant inductor Lr and resonant capacitor Cr continue to resonate, with the resonant current i... Lr Greater than the excitation current i Lm The secondary diode D6 continues to conduct.

[0035] Mode 5 [t4~t5]: At time t4, the current in Lr is equal to the current in Lm, the secondary rectifier diode D6 is turned off with zero current, the output voltage no longer clamps the primary winding of the transformer, Lm becomes a free resonant inductor and participates in the resonance. The magnetizing inductance Lm, the resonant inductance Lr, and the resonant capacitor Cr form a series resonant circuit with a resonant frequency of During resonance, due to the large excitation inductance Lm, the resonance period is very large. During this stage, the resonant current is consistent with the excitation current and is approximately constant.

[0036] Mode 6 [t5~t6]: At time t5, Q3 is turned off, entering the dead time. Excitation current i Lm Charge the junction capacitance of Q3 and discharge the junction capacitance of Q2 until the voltage across the junction capacitance of Q2 drops to zero.

[0037] As a simple replacement for this embodiment, the input AC power supply can be changed from two-phase AC to three-phase AC. The inductor Lr in Embodiment 1 can also be integrated into the transformer T1, and the MOSFET Q1 can be adjusted from the DC negative terminal side to the DC positive terminal side in Embodiment 1. The rectifier diode D6 of the transformer secondary winding can also be replaced with a MOSFET to achieve synchronous rectification of the output, etc. As long as the Buck-Boost circuit of the power conversion device includes two switching transistors Q1 and Q2, and one of the switching transistors Q2 is multiplexed as the lower transistor of the AHB flyback circuit, no matter how the other parts are modified, it is a simple replacement for this embodiment.

[0038] The above description is only a preferred embodiment of the present utility model, but the design concept of the present utility model is not limited thereto. Any non-substantial modifications made to the present utility model by those skilled in the art within the scope of the technology disclosed in the present utility model using this concept shall be deemed as an infringement of the protection scope of the present utility model.

Claims

1. A single-stage converter integrating Buck-Boost and AHB flyback circuits, characterized in that: It includes a Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit includes two switching transistors Q1 and Q2, and one of the switching transistors Q2 is multiplexed as the upper transistor of the AHB flyback circuit.

2. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 1, characterized in that: The switching transistors Q1 and Q2 are simultaneously turned on or off.

3. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 2, characterized in that: The AHB flyback circuit also includes a lower transistor Q3, which has the opposite state to Q1 and Q2.

4. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 3, characterized in that: The switching transistors Q1, Q2 and the lower transistor Q3 are controlled by PWM or PFM.

5. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to any one of claims 1-4, characterized in that: It also includes a rectifier bridge, whose AC input terminal is connected to an AC power supply, and whose DC output terminal is connected to a high-frequency transformer T1 through the Buck-Boost circuit and the AHB flyback circuit.

6. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 5, characterized in that: The two ends of the secondary winding of the high-frequency transformer T1 are connected through diode D6 and resistor R1; resistor R1 is connected in parallel with capacitor C2.

7. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 5, characterized in that: One end of the primary winding of the high-frequency transformer T1 is connected to a resonant circuit consisting of an inductor Lr and a capacitor Cr connected in series.

8. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 7, characterized in that: The resonant frequency of the resonant circuit is , and Lm is the magnetizing inductance.

9. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 3, characterized in that: The switching transistors Q1, Q2 and the lower transistor Q3 are power MOSFETs.

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